1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. The present invention also relates to a process, a machine, a manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a driving method thereof, or a manufacturing method thereof.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A transistor, a semiconductor circuit, an arithmetic device, a memory device, an imaging device, an electro-optical device, a display device, a light-emitting device, an electric storage device, and a power generation device (including a thin film solar cell, an organic thin film solar cell, and the like) each may include a semiconductor device.
2. Description of the Related Art
A technique in which a transistor is formed using a semiconductor material has attracted attention. The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device. As semiconductor materials applicable to the transistor, silicon-based semiconductor materials have been widely used, but oxide semiconductors have been attracting attention as alternative materials.
For example, a technique for forming a transistor using zinc oxide or an In—Ga—Zn-based oxide semiconductor as an oxide semiconductor is disclosed (see Patent Documents 1 and 2).
In recent years, demand for integrated circuits in which semiconductor elements such as miniaturized transistors are integrated with high density has risen with increased performance and reductions in the size and weight of electronic devices.